Minimized-thickness angular scanner of electromagnetic radiation

ABSTRACT

A minimized-thickness angular scanner of electromagnetic radiation includes an optical sandwich having a two-dimensional (2D) image source, and a scanning assembly that includes a first optic and a second optic, wherein at least one of the first optic and the second optic are oscillatorily translating. Translation of the optics provides for generation of a three-dimensional (3D) image, while the optical sandwich design provides for compact implementation of 3D displays.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/380,296 filed Apr. 26, 2006 and entitled “MINIMIZED-THICKNESS ANGULARSCANNER OF ELECTROMAGNETIC RADIATION,” which claims priority to U.S.Provisional Patent Application No. 60/675,165, filed Apr. 27, 2005 andentitled “Minimized-thickness angular scanner of electromagneticradiation,” the entirety of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Compact, wide-angle radiation-steering devices are valuable in fieldssuch as information display, optical communications, and laser-steering.The electromagnetic radiation can be of any frequency, such as visibleradiation or infrared. The embodiments discussed in this disclosurepertain to three-dimensional (3D) image display, particularly toview-sequential autostereoscopic three-dimensional display.

One class of methods for producing the perception of an “aerial” 3Dimage is known as multi-view autostereoscopic display. These methodstypically create 3D imagery, visible to the unaided eye (i.e. they donot require the use of polarized glasses), created by projectingmultiple depictions of the desired scene as rendered from a series ofviewpoints, usually as rendered by a computer-graphic camera movingalong a horizontal track.

3D displays have taken many forms, such as parallax panoramagrams whichuse lenticular display elements (“lenticules”) or parallax barriers tospatially demultiplex and steer light from an image surface to one ormore viewing regions. Lenticules may be biconvex, or made of multiplesurfaces, and may alternatively be long, thin lenses having a flatsurface on one side and an opposing curved surface, forming aplano-convex lens. When viewed, the lenticule may provide a viewangle-dependant striped or sliced portion of an image positioned behindeach lenticule (i.e., the slice that is viewable is dependent upon theangle from which the viewer views the image).

Therefore, arrays of lenticules can be used to create a parallax effectwherein different views or slices of total images are apparent fromdifferent viewing angles. In this way, a 3D effect can be achieved ifthe components of a 3D image are successfully rendered as separateslices, presented at the image surface as spatially multiplexed views,and are viewed through a lenticular array in a parallax manner.

The lenticular array concept has been used to create “no 3D glassesrequired” or “autostereoscopic” displays. Typically, such displays use asheet array of lenticular lenses to steer interdigitated left,intermediate and right eye views to a properly positioned observer.

Lenticular 3D displays techniques deserve their own category becausethey have earned a competitive place in the commercial market. However,the number of views they are capable of displaying is usually limitedbecause they employ spatial-multiplexing, whereby the resolution of thedisplay is sacrificed to include parallax information. The minimum pixelsize is consequently a limiting factor in these displays.

Interactive electronic flat panel 3D displays have been developed basedon these techniques.

For example, StereoGraphics Corporation (San Rafael, Calif.) sells theSynthaGram™ flat panel monitor series which is a lenticular-based 3Ddisplay. The SynthaGram series ranges from XGA (1024×768 pixel) to UXGA(3840×2400 pixel) monitors, and employs a custom fabricated diagonallenticular screen which divides pixels into 9 different views. Themonitor is driven by the DVI data output of a graphics card. Thelenticular screen is designed to eliminate moire fringing, which canoccur in lenticular flat panel screens, and divides pixels on the RGBlevel.

The drawback of existing lenticular 3D displays, and allspatially-multiplexed multi-view 3-D displays, is that by definitionthey trade off the projector's spatial resolution for the number ofviews displayed. The number of views is also limited by the shape of thelenticular elements and the pixel size. To date lenticular displays haveproduced at most 12 views. Furthermore, existing lenticular displayshave typically been implemented using components that are relativelylarge or stationary, and do not support mobile operation.

A requirement common to view-sequential displays is beam steering, whichcan be performed by a rotating mirror, a translating transparent columnon a black background in the system's Fourier plane, or other methods.

Several applications, such as mobile graphics visualization (i.e.quasi-holographic aerial imagery projected from a mobile phone orportable media device) and desktop 3-D visualization, require the 3-Ddisplay to be “thin.”

What is needed is a compact radiation steering device that is amenableto mobile operation (such as in a handheld device) that consumes andemits less power that prior art approaches. Preferably, the radiationsteering device can be fabricated from low-cost components and is usefulin tight spaces.

SUMMARY OF THE INVENTION

Disclosed is a display apparatus for projecting a three-dimensional (3D)image, including a two-dimensional (2D) image source; a first optic; asecond optic that is oscillatorily translatable; wherein the 2D imagesource, the first optic and the second optic form an optical sandwich.

Also disclosed is a method for providing a 3D image, the methodincluding: operating a display apparatus for projecting athree-dimensional (3D) image, having a two-dimensional (2D) imagesource; a scanning assembly having a first optic and a second optic thatis oscillatorily translatable; wherein the illumination assembly, thespatial light modulator the first optical array and the second opticalarray form an optical sandwich; providing a series of viewpoints to thedisplay apparatus; controlling the spatial light modulator; andcontrolling the scanning assembly to simultaneously display the seriesof viewpoints and thus provide the 3D image.

Further disclosed is a computer program product stored on machinereadable media, the product comprising instructions for providing a 3Dimage, the instructions including instructions for operating a displayapparatus for projecting a three-dimensional (3D) image, having atwo-dimensional (2D) image source; a scanning assembly comprising afirst optic and a second optic that is oscillatorily translatable;wherein the illumination assembly, the spatial light modulator the firstoptical array and the second optical array form an optical sandwich;providing a series of viewpoints to the display apparatus; controllingthe spatial light modulator; and controlling the scanning assembly tosimultaneously display the series of viewpoints and thus provide the 3Dimage.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 is a perspective view of an embodiment of a handheld 3D display;

FIG. 2 is a top view of an embodiment of a handheld 3D display;

FIG. 3 is a diagram of a system for recording viewpoints;

FIG. 4 depicts aspects of 3D image formation using the 3D display;

FIG. 5 depicts aspects of a projector based system for generating 3Dimages;

FIG. 6 is a schematic view of an embodiment for a compact 3D display;

FIG. 7 is a schematic view of another embodiment for a compact 3Ddisplay;

FIG. 8A and FIG. 8B, collectively referred to herein as FIG. 8, depictaspects of a pupil forming mode and a telecentric mode, respectively;

FIG. 9A through FIG. 9D, collectively referred to as FIG. 9, depictaspects of collimation with translation of a second lenticule;

FIG. 10 depicts a role of a vertical diffuser;

FIG. 11 depicts aspects of complimentary hemispherical lens arrays;

FIG. 12A and FIG. 12B, collectively referred to herein as FIG. 12,depict an effect of parallax barrier arrays;

FIG. 13 depicts incorporation of a parallax slit barrier with a scanningassembly;

FIG. 14 depicts a further embodiment of the compact 3D display;

FIG. 15 depicts exemplary components for operation of the compact 3Ddisplay; and

FIG. 16 depicts an exemplary method for generating a 3D image with thecompact 3D display.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein is a compact radiation-steering device using an opticalsandwich for providing a three dimensional (3D) display. Implementationof the optical sandwich provides for certain advantages over existingdesigns. For example, several applications, such as mobile graphicsvisualization (i.e. quasi-holographic aerial imagery projected from amobile phone or portable media device) and desktop 3D visualization,require the 3D display to be “thin.” The teachings herein provide forseveral “thin” radiation-steering devices, each referred to as a“compact 3D display.”

The compact 3D display as well as the methods for use thereof providebenefits that include, among other things, image generation that isamenable to mobile operation and may be implemented in handheld devices.The compact 3D display typically consumes and emits less power thanother techniques for producing 3D images. Advantageously, the compact 3Ddisplay can be fabricated from low-cost components and also fit intotight spaces.

The compact 3D display provides, in general, a compact form for steeringelectromagnetic radiation to produce a display of the 3D image. Thefollowing discussion explains the concept as it pertains to the compact3D display.

FIG. 1 illustrates a 3D image (10) that is a quasi-holographic imageprojected by a compact radiation steering device, referred to as thecompact 3D display (20). The compact 3D display (20) is incorporatedinto a 3D system (30). Exemplary implementations of the 3D system (30)include a handheld media device, a mobile telephone, a personal digitalassistant, an automotive dashboard mapping system, a global positioningsystem (GPS) receiver, a personal gaming device, an MP3 player, apersonal video player, a notebook computer (i.e., laptop) and othersimilar systems.

In an exemplary embodiment, the compact 3D display (20) is about 4.0″(102 mm) in width by about 2.0″ (50.8 mm) in height. In this embodiment,the 3D image (10) extends about 1″ (25.4 mm) into the 3D display (20)and about 1″ (25.4 mm) out of the 3D display (20), for a total depth ofthe 3D image (10) is about 2″ (50.8 mm). In some embodiments, such aswhere a high degree of quality control is used during fabrication of thebeam-steering optics, the total depth of the 3D image (10) is about 4″(101.6 mm).

Typically, the compact 3D display (20) comprises a rectangular displayhaving a diagonal dimension of about 1″ (25.4 mm) up to about 24″ (610mm). A variety of image aspect ratios may be used as considereddesirable (e.g., a 16:9 ratio).

In this exemplary embodiment, a two-dimensional (2D) image source, has ameasurement of about 4.0″ (101.6 mm) by about 2.0″ (50.8 mm). Exemplaryaspects of the 2D image source might include an array of about 1,000pixels by about 500 pixels, thus providing a pixel pitch of about 0.004″(102 μm), which is about 250 pixels per inch.

In a typical embodiment, and as illustrated in FIG. 1, an observer (40)perceives the 3D image (10) because the observer's left eye (40L) sees adifferent image than the observer's right eye (40R). Typically, thedisplay surface (21) repeatedly projects about 30 to about 100 sets ofray trajectories (also referred to as “views”). The views can typicallybe seen by the observer (40) from a variety of viewpoints. Forsimplicity, FIG. 1 only depicts two views.

FIG. 1 depicts a display surface (21), which is defined for mathematicalconvenience, and is the surface from which rays emanate. FIG. 1 alsodepicts a coordinate system, in which the x and y axes are coplanar tothe display surface (21) and the z axis is normal to the display surface(21). In a horizontal-parallax-only mode, the x axis is parallel to thehorizon and to the line connecting the observer's pupils.

FIG. 2 provides a top view of the situation depicted in FIG. 1. Again, a3D scene (10) is projected from the display surface (21) of the 3Ddisplay (20). An approximate measure of the horizontal viewing angle ofthe 3D image (10) is a viewing zone (50). Here, the horizontal angularextent of the horizontal viewing zone (50) is defined as the radiativeangular extent of a typical pixel (51) in a plane parallel to the xzplane. Here, the 3D image (10) is visible to the first observer (40) anda second observer (41) but not to a third observer (42).

So far the discussion has assumed the 3D display (20) provides ahorizontal-parallax-only (HPO) display. It may instead be a fullparallax display, in which case a vertical viewing zone could be definedand would have vertical parallax viewing qualities.

FIG. 3 illustrates a generalized process for computing and depicting 3Dimages (10) using a multi-view methodology. Projection of multi-view 3Dimages typically follows several steps. First, view-specific data areacquired from a set of physical or computational (synthetic) “cameras.”For example, in FIG. 3, a desired scene (22) of a flower in a flowerpotis illustrated. A series of computer-graphic cameras (23) compute theappearance of the desired scene (22) from a multitude of positions alonga horizontal track (24). Typically, about 30 to about 200 viewpoints arerendered and form a series of viewpoints (90). In this example, aleftmost image (100) and a rightmost image (199) are depicted. Imagesbetween the leftmost image (100) and the rightmost image (199) arerepresented by numbers between (100) and (199), wherein the referencenumbers are representative of succession in the series of viewpoints(90). Playback or reconstruction of the desired scene occurs when the 3Ddisplay (20) projects rays of visible light to several locations.

In this example, and with reference to FIG. 4, the left most image (100)is projected by a ray bundle (100′), an intermediate depiction (110) isprojected by a ray bundle (110′). In this case, bundles (100′) and(110′) each meet at an apex, or pupil when an observer places his lefteye (40L) at the pupil formed by bundle (100′) and his right eye (40R)at the pupil formed by bundle (110′), he sees images (100) and (110). Asa result, the observer perceives a floating 3D image in the vicinity ofthe 3D display.

FIG. 5 illustrates an embodiment of a view-sequential 3D display (20).The embodiment depicted is disclosed in the pending U.S. patentapplication Ser. No., 11/146,749, filed Jun. 7, 2005, published Dec. 8,2005 as publication no. 2005/0270645 A1, the disclosure of which isincorporated herein by reference in its entirety.

In the embodiment of FIG. 5, a 3D projection system (200) includes afirst lenticular lens array (230) and a second lenticular lens array(235), at least one of which undergoes low-amplitude reciprocatingtranslational movement to effect scanning. As depicted, the secondlenticular lens array (235) is subject to the translational movement.

In this embodiment, a projector (210) that projects the series ofviewpoints (80) for a desired 3D image (10) is provided. The projector(210) is typically controlled by standard electronics (aspects of whichare depicted in FIG. 15). Preferably, the projector (210) is capable offrame rates in excess of 5,000 frames per second. One exemplaryprojector (210) being a ferroelectric liquid crystal micro-displayavailable from DisplayTech (Colorado, USA). An aperture (215), in theform of a column that is oriented parallel to the y-axis, is placed infront of the projector (210). A focusing optic (220) re-images eachviewpoint from the series of viewpoints (80) to the surface of avertical diffuser (225) (or, optionally, to a Fresnel lens (222)). Notethat as used in this embodiment, “vertical” corresponds to theorientation of the y-axis. Other components may be included as deemedsuitable (such as, for example, polarizing and “analyzing” components).

The light passes through the first lenticular lens array (230) andsubsequently the second lenticular lens array (235). Typically, a lenspitch is approximately 75 lenses per mm, and a focal length isapproximately 300 microns for each of the first lenticular lens array(230) and the second lenticular lens array (235). A distance D betweenthe lenticular lens arrays is approximately 600 microns (about 2 F), asmeasured from the “tops” of the lenticular lenses in each array.Scanning motion is performed by rapidly translating the secondlenticular lens array (235) back and forth, with a travel path of about300 microns. This results in scanning light across a wide field, from apupil A (240A) to a pupil B (240B). It is important that the scanningmotion be synchronized to the series of viewpoints projected by theprojector (210). When that occurs, any observer within the viewing zoneof the 3D display (200) will perceive a 3D image.

The teachings herein incorporate aspects of U.S. patent application Ser.No., 11/146,749, while providing for certain advancements and distinctadvantages. Reference may be had to FIG. 6.

In FIG. 6, various components are used to provide for compactimplementation of the 3D display (20). In the embodiment depicted, anillumination assembly (300), such as a backlight, illuminates atransmissive spatial light modulator (SLM) (305) as the two-dimensional(2D) image source. In some embodiments, the light passes through anarray of invisible microlouvers (310) that function like verticalblinds, a vertical diffuser (315), and a scanning assembly that includesa first lenticular lens array (320), and a second lenticular lens array(325). In this embodiment, the second lenticular lens array (325) is anoscillatory translating lenticular lens array. It should be noted that avariety of embodiments for the 2D image source may be realized.

The fundamental image-generating component is the spatial lightmodulator (SLM) (305). This SLM (305) can be an emissive array such asan Organic LEDs (OLED) display panel, an array of micro-emitters such aslasers (e.g., vertical cavity surface emitting lasers, or VCSELs), areflective display, a transreflective display, or otherradiation-emitting module. If the image-generating component is areflective display, it may be illuminated using methods well-known tothose skilled in the field of microdisplay system engineering (refer toFIG. 14).

It should be recognized that use of or reference to the spatial lightmodulator SLM (305) is a non-limiting and merely exemplary embodiment.More specifically, one skilled in the art will recognize that the SLM(305) modulates incident light into patterns, while an emissive arraymay be used to directly create the patterns. In either case, andregardless of technique, the 2D image source provides for generation ofa 2D pattern. Accordingly, the teachings herein are not limited to theapparatus disclosed herein in regard to the 2D image source and mayinclude other devices as practicable.

An exemplary embodiment for the microlouvers (310) are Vikuiti LightControl Films model numbers LCF-P 98-0440-2658-3 and ALCF-P98-0440-4264-0, available from 3M Corporation (Minneapolis, Minn.).

A variety of components may be used as the 2D image source. Anon-limiting example includes an emissive array of Organic LEDs (OLEDs),which deliver thin, power efficient and bright displays with fastswitching speeds). Other non-limiting examples include a spatial lightmodulator (e.g., a transmissive LCD panel, typically a transmissiveferroelectric LCD panel in combination with associated polarizingfilters and analyzing filters). Exemplary OLED arrays include thoseavailable from Samsung Corporation, Emagin Corporation of BellevueWash., Kodak Corporation of Rochester, N.Y. and Universal DisplayCorporation of Ewing N.J., while exemplary LCD-based light modulatorsinclude those available from Displaytech Ltd of Colorado and FourthDimension Displays (formerly CRL Opto), of Fife United Kingdom. LCDlight based modulators may further be used in conjunction with otherillumination systems, such as color LED backlighting.

Exemplary commercially available lenticular lens arrays include thoseavailable from Anteryon International B.V. and Microlens Technology,Inc. Exemplary commercially available components for use as optionaldiffusers and vertical diffusers include those available from PhysicalOptics Corp. and Dai Nippon Printing Co. Ltd of Japan.

For the exemplary embodiment, the 3D display (20) employs a refresh ratewhere scanning (i.e., oscillatory translation of at least one of thelens arrays) would occur left-to-right or right-to-left at a frequencyof about 60 Hz. In this embodiment, the 3D display (20) uses a screenthat is about 500 pixels by about 1,000 pixels, generates about 30“views” per quasi-holographic image, and has total image depth of about4″ (10.16 mm, rounded to 10 mm) using 256 colors.

Multi-color illumination is provided by the OLED array if OLEDs are usedfor the 2D image source. If non-emissive modulators are used, theillumination will typically use off-the-shelf components. For example,near-eye displays might use switched LED illumination—cycling red,green, and blue LEDs to illuminate the 2D image source. That is, oneskilled in the art will understand that the illumination assembly (300)may be arranged to provide a variety of predetermined wavelengths.

The lenticular lens arrays would typically have the same size and shapeas the 2D image source. For the exemplary embodiment, the lenslets havea focal length of about 800 microns and a lens pitch of about 300microns. The lens pitch does not have to equal the source pixel pitch.The lens array is usually fabricated from a sheet of glass, and istherefore at least about 0.5 mm thick to about 1.0 mm thick. That is,the lens array is about as thick as its focal length, and usually abutsor nearly abuts the 2D image source.

In this embodiment, the lens arrays translates about 125 microns backand forth. If the array moves too far, the first lens array will bleedunwanted light into an adjacent lens to a primary receiving lens on thesecond lens array, forming unwanted ghost images in the output. Itshould be that techniques are disclosed herein for controlling thisproblem.

If an optional barrier array (also called an “aperture array”) is used,the barrier array will typically have a pitch equal or approximatelyequal to the 2D image source pixel pitch (i.e., the pitch in the SLM(305)). That is, each pixel will be covered by a translucent window thatlimits the aperture of the pixel. This correlation serves two purposes.The correlation limits crosstalk between pixels thereby preventing ghostimages. This has the benefit of increasing the contrast of the image andtherefore improving the depth of the 3D image. Second, apertures arecommonly used to prevent the effects of lens aberrations making 3Dimages crisper, at the expense of loss of brightness.

For a number of embodiments, a vertical diffuser (315) is optional. Anexemplary embodiment for a vertical diffuser (315) includes thoseavailable from Physical Optics Corporation of Torrance, Calif. Typicalembodiments for the vertical diffuser (315) have a horizontal beamspread of approx. 0.1 degrees and a vertical beam spread of 90 degrees.In some embodiments, the vertical diffuser (315) is placed as close aspossible to the spatial light modulator (305) in order to minimize blurin the 3D image (10) associated with each pixel.

Typically, the first lenticular lens array (320) and second lenticularlens array (325) are separated by approximately 2 F (1.6 mm).

The “optical sandwich” that typically includes the components of FIG. 6,can be made “thin.” For example, the optical sandwich that provides forthe 3D display (20) is typically on the order of about 30 mm.Accordingly, the 3D display (20) is ideally suited for a variety ofmobile applications. Translation of the lenticular can be performed by anumber of techniques, such as the use of a flexure stage. FIG. 6 depictsan embodiment useful for a lenticular based system, while FIG. 7 depictsanother embodiment for implementing a hemispherical lens array or “fly'seye” system (refer to FIG. 11).

With reference to an “optical sandwich,” the components of the 3Ddisplay (20) are substantially close to each other or in contact withone another, and may, in some respects, be considered layers orsubstantially similar to layers. That is, substantial distances, such asdistances between components for focusing or providing for other opticalproperties are generally not required. For example, the distance betweenthe projector (210) and the scanning assembly is not called for. Itshould be noted that at least some distance between components of theoptical sandwich may be required. For example, in the case of atranslational lenticular lens array, at least some distance between astationary lenticular lens array may be called for (e.g., to provide forunrestricted translation thereof). In this regard, the optical sandwichprovides for the 3D display (20) having a minimized thickness.

Note that the 3D system (30) may be constructed such that, for a giveninstant in time, the ray bundles (100′, 110′) do not converge (i.e.,meet at an apex or pupil) but alternatively travel together in amutually “collimated” (i.e., telecentric) manner. In this alternative,at various instants in time, ray bundles exit the display surface 21having different trajectories, so that aggregated over the persistenceof vision, pupils do form at the locations shown. FIG. 8A and FIG. 8B,collectively referred to herein as FIG. 8, depict aspects of imageforming using the alternative techniques of a “convergence mode (i.e.,the “pupil forming mode”) and a “telecentric mode,” repectively

Referring to FIG. 8, aspects of the optics for the convergence mode andthe telecentric mode are depicted. In FIG. 8A, a ray diagram ispresented wherein the ray bundle converges at a location. In FIG. 8B,another ray diagram is presented wherein a collimated beam is producedand the resulting beam “sweeps” the viewing zone 50.

FIG. 9A through FIG. 9D depicts aspects of the telecentric mode, whereinarticulation of the second lenticular lens array (325) provides forredirecting the ray bundle (depicted as the grouped arrows). Variousinputs to the first lenticular lens array (320) may be used, includingmodulated illumination from the spatial light modulator (305), outputfrom optional microlouvers (310), and others. FIG. 9 generally depictsextrema for the ray bundle. In this example, the arrangement of thefirst lenticular lens array (320) and the second lenticular lens array(325) provide for an f-stop of about 800 μm while the pitch is about 300μm and the translational lens movement includes a horizontal translationof about 125 μm.

Note that in FIG. 9, oscillatory translation of the second lenticularlens array (325) occurs in an X direction (as depicted). In a furtherembodiment (see FIG. 11), oscillatory translation occurs in the Xdirection and a Y direction. Note that although translation may occur inthe Z direction (along a main optical path), such translation is notconsidered oscillatory and typically for purposes other than scanning.For example, translation in the Z direction may be undertaken forfocusing of the 3D image (10) or improving aspects of the viewing zone(50). In short, oscillatory translation generally occurs in at least onedirection that is not along the main optical path.

Further, note that in FIG. 9, a one-to-one correspondence exists forlenses in the first lenticular lens array (320) and the secondlenticular lens array (325). One skilled in the art will recognize thatthis is merely illustrative and not a limitation. In other embodiments,other ratios of lens populations may exist (e.g., 1.5:1, 2:1, etc, . . .).

FIG. 10 provides an illustration of the role of the vertical diffuser(315). In FIG. 10 a side view of the scanning assembly depicts avertical diffusion of the ray bundle when considered with reference tothe observer 40.

One skilled in the art will recognize that articulating both the firstlenticular lens array (320) and the second lenticular lens array (325)may be used to provide for a greater viewing zone 50 when compared toarticulation of a single element.

It may be said that the articulation of the optical components (e.g.,the first lenticular lens array (320) and the second lenticular lensarray (325)) are oscillatorily translatable. That is, whichever opticalcomponent is used for scanning will typically translate in a manner thatis considered to be substantially equivalent to oscillation. Oscillatorytranslation may occur in any pattern deemed suitable. For example, insome embodiments, translation is merely horizontal. In otherembodiments, translation follows a certain pattern. Reference may be hadto FIG. 11.

Referring to FIG. 11, aspects of another embodiment of a scanningassembly are shown. In the embodiment of FIG. 11, both the firstlenticular lens array (320) and the second lenticular lens array (325)are replaced with a first hemispherical lens array (420) and a secondhemispherical lens array (425), respectively. The first hemisphericallens array (420) and the second hemispherical lens array (425) forming ahemispherical scanning assembly (450). Note that in common parlance,each “hemispherical lens array” is referred to as a “fly's eye” array.

The hemispherical scanning assembly (450) may be used advantageously toprovide for full-parallax 3D displays (or equivalently two-axis beamsteering). Clearly, the first hemispherical lens array (420) is inoptical communication the second hemispherical lens array (425).Scanning can be achieved by moving the first hemispherical lens array(420), second hemispherical lens array (425), or both lens arrays (420,425).

The oscillatory translating of the optical elements may follow any oneor more of a horizontal path, a vertical path, a zig-zag path and acircuitous path (meaning any other type of path desired). For example,FIG. 11 depicts a zig-zag path for the oscillatory translation.

Use of the hemispherical scanning assembly (450) provides for furtheradvantages in that a scanning path 475 may include a vertical component(y axis) as well as the horizontal component (x axis).

In other embodiments, optical elements used in the scanning assemblyinclude, without limitation, lenticular elements, holographic opticalelements (HOE), at least one irregular lens array, a “parallax” barrierarray, an optical wedge and a prismatic optic as well as otherradiation-steering component and a radiation-blocking component.

As an example, the use of parallax barrier arrays as scanning elementsis shown in FIG. 12. In the embodiment depicted in FIG. 12, a firstbarrier array (520) and a second barrier array (525) are used in placeof the first lenticular (320) and the second lenticular (325) for thescanning assembly. In FIG. 12A, the ray bundle proceeds directly throughthe scanning assembly, while in FIG. 12B, the ray bundle is steered bytranslation of the second barrier array (525).

FIG. 13 depicts use of a single barrier array (520) in combination withthe first lenticular array (320) and the second lenticular array (325).In this embodiment, the barrier array (520) typically includes anaperture associated with each lens that is designed to account for andminimize aberrations and crosstalk from adjacent pixels.

FIG. 14 depicts a further embodiment of the compact 3D display 20. Inthis embodiment, a beam splitter (345) is incorporated. Use of the beamsplitter (345) provides for various advantages, such as the use ofexternal illumination in combination with a reflective display. The useof external illumination may be useful for various purposes, such as toenhance brilliance in the image plane.

FIG. 15 depicts aspects of an exemplary embodiment of controlelectronics (261) for driving the compact 3D display (20). The controlelectronics (261) typically include the scanning assembly (55), where atleast one of the first lenticular array (320) and the second lenticulararray (325) are coupled to a motive force (60) for driving translationalmovement. In this embodiment, translation is controlled by a PID(proportional-integral-derivative) controller (80) that monitors themotion of the scanning assembly (55) using a diffractive motion encoder(81), and which, for example, drives a “voice coil” motor. The detailsof the PID control loop would be well-understood to those skilled in thefield of servo control electronics and are therefore not discussed atlength herein.

Typically, a core rendering electronics subassembly (82) assists ingenerating a sequence of 2-D perspective views projected by a fastSLM-based microdisplay (305). The core rendering electronics (82) alsoreceives velocity and position data from the PID controller (80) controlloop. In this case, the core rendering electronics (82) are slaved tothe scanning assembly (55). Alternatively, the core renderingelectronics (82) can act as master to the scanning assembly (55).

It is significant that the scanning assembly (55) undergoes time-varyingoptical properties, and that the SLM (305) is located adjacent to thescanning assembly (55) to shine light on or through the scanningassembly (55) in order to produce the 3D image.

It should be noted that the scanning assembly (55) may spend asignificant interval of time at the extremes of a scan path. It isunderstood that, at least in some instances that if light passed throughthe screen during those intervals, the light would be too bright to bedisplayed properly. Therefore, “blank” (black) data are typically loadedinto the 2D image source for the extreme views. As an illustration, fora sweep path having fifty positions, a forty-ninth clock is used totrigger a pre-load of a black screen for those views.

It should be noted that references to the term “lenticular” should beinterpreted to include other methods for using spatial multiplexing toencode two or more views of a 3D image (10) into a single 2D field ofpixels. These “panoramagrams” or “parallax displays” can use manyoptical devices to perform demultiplexing, such as lenticular sheets,parallax barriers, fly's-eye lens arrays, or holographic opticalelements. The teachings herein generally provide for employinglenticular arrays and other optical arrays for a time-multiplexed mannerrather than or in addition to a spatially-multiplexed manner.

An exemplary method for providing the 3D image (10) is depicted in FIG.16. Providing the 3D image (500) typically calls for selecting the 3Dsystem (501), providing a series of viewpoints (502) to the 3D system(30), controlling the 2D image source (503), controlling the scanningassembly (504) for simultaneously displaying the series of viewpoints(505), thus providing the 3D image.

Selecting the 3D system (501) calls for selecting the 3D system (30)that includes appropriate components and features for producing thedesired type of 3D image (10). For example, size, color, resolution,scan rate and other features may be considered when selecting the 3Dsystem (501).

Providing the series of viewpoints (502) typically calls for assemblinga series of viewpoints (90) produced in a manner that is generallyconsistent with the manner discussed above with reference to FIG. 3, ormay involve some equivalent thereto. The series of viewpoints (90) istypically provided by electronics as depicted in FIG. 15, or by someequivalent thereto.

Controlling the 2D image source (503) and controlling the scanningassembly (504) similarly call for using the control electronics (261) togenerate at least one 2D image in the spatial light modulator (305) andto drive the oscillatory translations of the optics.

When controlling the 2D image source (503) and controlling the scanningassembly (504) are properly executed, simultaneous displaying the seriesof viewpoints (505) is achieved, thus providing the 3D image (500).

Of course, with regard to the term “simultaneous”, this should not betaken literally. That is, it should be recognized that scanning isrequired. However, in typical embodiments, the scan rate is fast enoughto provide an illusion of the 3D image (10) to the unaided human eye. Itshould be recognized that observation of the 3D image (10) with otherdevices (such as a video camera) may alter or destroy the perception ofa continuous display.

Stated another way, the oscillatory motion of at least one of theoptical elements includes an oscillation of a high enough frequency thatincremental display of each viewpoint (90) from the series of viewpointsis substantially completed within an integration period for the humaneye.

One skilled in the art will recognize that methods for providing the 3Dimage (500) may vary greatly. For example, in one embodiment,controlling the 2D image source (503) and controlling the scanningassembly (504) calls for operating the 3D system (30) in thepupil-forming mode. In another embodiment, the controlling the 2D imagesource (503) and controlling the scanning assembly (504) calls foroperating the 3D system (30) in the telecentric mode. Other embodimentscontemplate operation of or accounting for certain additional componentssuch as the microlouvers (310), the vertical diffuser (315) and othersuch aspects, some of which are described herein.

One skilled in the art will appreciate that the invention can bepracticed by other than the described embodiments, which are presentedfor purposes of illustration and not of limitation. Thus, equivalentsare envisioned and encompassed by this disclosure.

What is claimed is:
 1. A system, comprising: a projector configured toproject a set of images associated with different perspectives of ascene; and a controller configured to control linear translation of anoptic relative to another optic in first and second coplanar directionsand in synchronization with the set of images projected by the projectorbased at least in part on data received from a feedback control loop togenerate a three-dimensional image.
 2. The system of claim 1, whereinthe optic is periodically translated relative to the other optic in thefirst and second coplanar directions.
 3. The system of claim 1, whereinthe optic is translated relative to the other optic in the first andsecond coplanar directions in an oscillatory manner.
 4. The system ofclaim 1, wherein at least one of the optic or the other optic comprisesa lenticular lens array.
 5. The system of claim 1, wherein the opticcomprises an oscillatory translatable optic.
 6. The system of claim 1,wherein a path for the optic comprises a zig-zag path.
 7. The system ofclaim 1, wherein a path for the optic comprises an indirect path that isnot along the first and second coplanar directions.
 8. The system ofclaim 1, wherein the projector comprises a transmissive liquid crystaldisplay (LCD) panel.
 9. The system of claim 8, wherein the transmissiveLCD panel comprises at least one of a polarizing filter or an analyzingfilter.
 10. A method, comprising: projecting a set of images associatedwith different perspectives of a scene; and generating athree-dimensional image from the set of images by controlling lineartranslation of an optic relative to another optic in first and secondcoplanar directions and in synchronization with the set of images basedat least in part on data received from a feedback control loop.
 11. Themethod of claim 10, wherein the generating the three-dimensional imagefrom the set of images comprises periodically translating the opticrelative to the other optic in the first and second coplanar directions.12. The method of claim 10, wherein the generating the three-dimensionalimage from the set of images comprises oscillating the optic relative tothe other optic in the first and second coplanar directions.
 13. Themethod of claim 10, wherein the generating the three-dimensional imagefrom the set of images comprises translating the optic via a zig-zagpath.
 14. The method of claim 10, wherein the generating thethree-dimensional image from the set of images comprises translating theoptic via an indirect path that is not along the first and secondcoplanar directions.
 15. The method of claim 10, wherein the generatingthe three-dimensional image from the set of images comprises oscillatingthe optic relative to the other optic at a frequency to incrementallydisplay a viewpoint associated with the set of images within a definedintegration period.
 16. The method of claim 10, further comprisingprojecting the three-dimensional image to a display surface.
 17. Acomputer readable storage device comprising executable instructionsthat, in response to execution, cause a system comprising a processor toperform operations, comprising: projecting a set of images associatedwith different perspectives of a scene; and generating athree-dimensional image from the set of images by controlling lineartranslation of an optic relative to another optic in first and secondcoplanar directions and in synchronization with the set of images basedat least in part on data received from a feedback control loop.
 18. Thecomputer readable storage device of claim 17, wherein the generating thethree-dimensional image from the set of images comprises periodicallytranslating the optic relative to the other optic in the first andsecond coplanar directions.
 19. The computer readable storage device ofclaim 17, wherein the generating the three-dimensional image from theset of images comprises oscillating the optic relative to the otheroptic in the first and second coplanar directions.
 20. The computerreadable storage device of claim 17, wherein the generating thethree-dimensional image from the set of images comprises translating theoptic via an indirect path that is not along the first and secondcoplanar directions.